The Liberal Democrat business secretary, Vince Cable, and the Treasury's chief secretary, Danny Alexander, stepped into the bankers' bonuses row today, saying banks will have to show restraint, as David Cameron promised he will deliver a deal that includes lower bonuses, higher lending and higher taxes.

Lord Oakeshott, a Lib Dem Treasury spokesman, also insisted his party had not given up the fight with the banks, and negotiations were continuing.

Cable said: "I'm very hopeful of getting a balanced agreement with the banks which … deals with lending to small businesses, better disclosure, a genuine contribution to the economy and real bonus restraint. They would be very wise to approach these discussions seriously."

He stressed "nothing has been removed from the table" by the government, including the threat of a new bonus tax.

Alexander made a similar promise, saying such a tax had not been ruled out. The Treasury, however, had made its priority an increase in bank lending.

The coalition was hit by reports that Eric Daniels, the boss of Lloyds, which is partly owned by the taxpayer, was set to leave with a £2m bonus. He agreed in the previous two years to forgo any bonus.

Ministerial sources continued to insist the focus in private talks with the banks lay on an agreement that sees a net increase in lending to businesses.

In the Commons, Cameron and Ed Miliband clashed over bankers' bonuses as the prime minister was accused of applying "one rule for the banks and another for everybody else".

• This article was amended on 13 January 2011. The original said that Eric Daniels was due to leave with a £2bn bonus. This has been corrected.